The action of anthracite and bituminous coal dusts mixed with quartz on the lungs of rats.

Belt and King (1945) studied the tissue reactions produced in animals by selected dusts from South Wales coal mines, and found that clean coal (low ash coal fraction containing 99% coal) produced only minimal fibrosis (grade 1) with simple foreign body reaction in 250 to 500 days. In experiments with high ash coal fractions which contained from 37 to 66% coal and about 1 to 3% quartz, the rest being kaolin and mica, grade 1 fibrosis was also produced in 250 days; and the reticulin was slightly denser in character, although it could not be classified as grade 2 fibrosis. In their experiments with airborne dusts, they examined 14 samples from six different mines, which included anthracite mines with both a high and low incidence of silicosis, and also steam coal and bituminous coal mines. Nine of these samples produced only a simple foreign body reaction with grade 1 fibrosis, the average coal content of these nine samples being 85%, and the average siliceous mineral content 13%. The remaining five samples produced something more than a foreign body reaction, and fibrosis was of grades 2 and 3. These dusts averaged 74% of coal and contained 39, 28, 14, 17, and 15% (average 22%) of siliceous minerals, there being a considerable overlap between the two groups. Further studies were made using artificial mixtures of airborne mine dusts with amounts of pure quartz which were varied from 19 to 28%, and in one case made as high as 51 %. In all these experiments, at the end of one year, the fibrosis was of grade 4 type, and no difference could be found between anthracite and bituminous coal mine dusts. In our present experiments airborne dusts from an anthracite coal mine and a bituminous coal mine have been used. These have much higher ash contents (mainly kaolin and mica) than the coal dusts used by Belt and King. They were mixed with 10% and 30% of commercial quartz of known pathogenicity in order to determine if variable amounts of quartz give variable degrees of fibrosis in the presence of these large amounts of airborne mine dusts; whether airborne dust has any modifying effect on the quartz; and, if so, whether there is a difference between the anthracite and bituminous coal in this respect.